What should you know?
A simple kidney cyst is a benign fluid-filled sac that becomes more common with age. It usually does not damage kidney function and often needs no treatment.
A cyst with thick or irregular walls, septa, calcification, a solid component or interval change needs closer assessment. Contrast-enhanced CT or MRI may be needed for formal risk classification.
Common symptoms and signs
- No symptoms in most cases
- Flank discomfort when a cyst is large
- Blood in the urine in uncommon cases
- Fever and tenderness if infected
Diagnosis and the role of ultrasound
Ultrasound identifies the classic features of a simple cyst and records size, location, wall, contents and blood flow. Complex features should trigger appropriate additional imaging.
- Thin wall and clear-fluid appearance
- Septa, calcification or solid tissue
- Pressure on urinary drainage
- Both kidneys and collecting systems
Treatment and next steps
A typical asymptomatic simple cyst often needs no treatment. Pain, infection, obstruction or complex morphology should be evaluated by a urologist.
When is urgent care needed?
- Severe flank pain with fever
- Visible blood in urine or markedly reduced urine output
- Pain with dizziness or fainting